Cyclic keto esters and lubricants containing them



United States Patent 3,313,732 CYCLIC KETO ESTERS AND LUBRICANTSCONTAINTNG THEM Keith Coupland and John Pennington, Hull, and SidneyJohn Branch, Horusea, England, assignors to The DllS- tillers CompanyLimited, Edinburgh, Scotland, :1 British company No Drawing. Filed Nov.12, 1954, Ser. No. 410,772 Claims priority, application Great Britain,Nov. 28, 1963, 46,968/63; Apr. 1, 1964, 13,512/64 1 Claim. (Cl. 252-57)This invention relates to synthetic lubricants and in particular tosynthetic lubricant bases.

Synthetic lubricant bases may comprise, for example, esters such asdioctyl and dinonyl sebacates. In order to fulfill completely therequirements of a practical lubricant composition, various additives arecustomarily added to the base, which normally constitutes at least 60%and more, usually at least 90% by weight of the lubricant composition.Such additives include antioxidants (for instance phenothiazine ordioctyl phenothiazine); viscosity index improvers (for instancepolymethacrylates or polyglycolethers); load carrying additives (forinstance tritolyl phosphate or trixylyl phosphate), metal de-activatorsand anti-corrosion agents. The nature and quantity of such additives arevaried as required for any particular lubricant composition to fulfillspecific desiderata.

The present invention provides a synthetic lubricant base containing atleast one keto-ester of formula:

CH2. CH2.C ozR CCH2. CH2. C 02R wherein R R R and R are the same ordifferent alkyl groups, each of preferably from 4 to 16 carbon atoms,and R is an alkyl group such as the methyl group.

These compounds may, with advantage, be used as synthetic lubricantbases in admixture with a compound having at least two ester groupingsin the molecule, such as the alkyl esters of organic dicarboxylic acidsand monocarboxylic acid esters of polyalcohols. It is contemplated thathalogen-substituted esters are also useful as compounds having at leasttwo ester groupings in the molecule.

3,313,732 Patented Apr. 11, 1967 Accordingly the present inventionfurther provides a synthetic lubricant base composition comprising atleast one keto-ester of formula ice H2CCH2 wherein R R R R and R are ashereinbefore defined, in admixture with a compound having at least twoester groupings in the molecule.

Suitable compounds having at least two ester groupings in the moleculeinclude dioctyl sebacate, dinonyl sebacate, esters of trimethylolpropane such as trimethylol propane tricaprylate and esters ofpentaerythritol.

The proportions of keto-ester and compound having at least tWo estergroupings in the molecule in the synthetic lubricant bases of theinvention will, naturally, vary within wide limits according to therequirements for the particular base to be formulated. Suitableproportions are Within the range to 10%, especially 70% to 25%,particularly 30-35% of keto-ester by weight of the total base.

The keto-esters employed in the synthetic lubricant bases of theinvention can be prepared for example by cyanoethylation of theappropriate cycloalkanone or alkylsubstituted cycloalkanone, followed byhydrolysis of the resulting tetraor tri-nitrile, to give thecorresponding acid. Such a reaction is described for specific compoundsin J. Amer. Chem. Soc., 64, 2850-2858. The acid is then esterified witha small excess of the appropriate alcohol together with entrainer and anesterification catalyst. The reaction conditions are selected to giveesterification temperatures within the range of C. to 180 C., preferablybetween C. and C. High temperatures Within the quoted ranges do notsignificantly affect ester yield or quality, but are useful in promotingsatisfactory reaction rates. The entrainer may be for example benzene,toluene, cyelohexane or any other hydrocarbon capable of forming abinary azeotrope with Water. The alcohol used may be any saturatedaliphatic or cycloaliphatic alcohol having from 1 to 16, preferably 4 to16 carbon atoms. The excess of alcohol employed in the esterification issuitably at least 2% and preferably 313% based on the Weight of acid.Any of the known esterification catalysts may be used, but sulphuricacid is preferred. The amount of catalyst used depends on the purity ofthe acid to be esterified, but generally 0.05 to 1.0% W./ W. sulphuricacid based on the total esterification charge is satisfactory.

The crude ester is generally dark brown in colour and can bedecolourized by ozone, potassium permanganate, bromine or sodiumhypochlorite, but it is preferred to wash the crude ester with 2 X Avolumes of aqueous 10% w./v. sodium hydroxide solution, l x A volume ofaqueous 10% w./v. sodium chloride solution and l X A volume of distilledwater. Sodium hydroxide solutions of less than 5% w./v. are lesseffective decolourants and significant improvements are not obtained bythe use of odium hydroxide solutions of greater concentration than w./v.

Some of the keto-esters of which the preparation has been describedabove are new compounds. Accordingly the present invention still furtherprovides keto-esters of wherein R R R and R have the meanings ascribedIt may be seen from the table that keto-esters of this invention havevery good oxidative stability and thermal volatility and possessadequate viscosity at 210 F., and adequate low temperature fluidity.

Example 7 A mixture of 70% of the keto-ester of Example 3 With 30% ofdioctyl sebacate was evaluated according to the above procedure. It hadthe following properties:

Oxidative stability, percent W./W. loss 26 Thermal volatility, percentw./w. loss 3 Viscosity increase Nil Viscosity at 210 F., centistokes 8.6Pour point, F. -65

Example 8 A mixture of 55% of the keto-ester of Example 3 with 45% ofdinonyl sebacate was evaluated according to the procedure described inExample 1 in respect of oxidative stability, viscosity and pour point.The results were as follows:

Oxidative stability, percent weight loss Viscosity at 210 F.,centistokes 7.8 Viscosity at 100 F., centistokes 52.1 Pour point, F.Below 60 The normal volatility of this material was assessed in similarmanner to that used in Example 1 but under more severe conditions, sincethe temperature of the ester was maintained at 340 C. The thermalproperties of this material at this temperature are shown in Table 2,together with the properties of dinonyl sebacate.

TABLE 2 Thermal volatility (340 C.) After test Ester Weight Acid N 0.,

loss, Viscosity increase Mg. KoH/g. Appearance percent Dinonyl sebacate36 Material solidified, 238 Solid. 55% Ester 4, dinonyl sebacate. 27Small 36 Slight darkening.

The invention is illustrated by the following examples in whichoxidative stability was assessed by the method of the American Standardfor the Testing of Materials No. D972-56, except that for Examples 4 to6 the test temperature used was 500 F. Viscosities and pour points weredetermined by conventional methods, and the measurement of thermalvolatility was made by passing nitrogen through the sample at two litresper hour for 6 /2 hours (6 hours in the cases of Examples 4-6) at atemperature of 300 C.; the loss in weight, the appearance and theincrease in viscosity of the samples were noted at the end of the test.

Examples 1-6 A comparison of the properties of keto-esters in ac-Example 9 A mixture of 45% of the keto-ester of Example 4 with ofdioctyl sebacate, with the addition of 3% of a polymeric methacrylateviscosity index improver had the following properties:

Oxidative stability, percent weight loss 51 Viscosity at 210 F.,centistokes 7.6 Viscosity at 100 F., centistokes 39.6 Pour point, F.Below Example 10 A mixture of of the keto-ester of Example 4 with 35% oftrimethylol propane tricaprylate had the following properties:

cordance with the invention having a structural formula OxidativeStability, P Weight 1055 26 containing a cyclohexanone ring with th ofdi l Viscosity at 210 F., centistokes 8.0 sebacate and those of anotherketo-ester of th i ve ti 60 Viscosity at F., centistokes 52.2 are Shownin the following Table 1. Pour point, F. -60

TABLE 1 Oxidative Thermal volatility Examplc/ Stability Viscosity atPour COIHIJHI'ISOII Ester Weight loss 210 F. Cenpoint, Number (percent)Weight loss Viscosity tistokes F.

(percent) increase A Dinonyl seh'ira tP 79 12 7 4. 6 8O Esters of thisinvention:

R R R R =n-Butyl 15 15 Nil 10. G -35 R ,R ,R and R mixed C 0 a 15 6 Nil17. 0 -15 R R R R =2-etliyllicxy1 l6 6 Nil 14. 4 20 R ,R ,R and R mixedC3, C nlkyL. l4 6 Nil 12. 0 30 R ,R ',R =ri-butyl, R =1uetlryl 28 -101,l,3,3 tetra(n-butyl-fl-propionnte) cyclopeutan-2-one 6 Example 11 Amixture of 33% of the keto-ester of Example 1 with 66% of trimethylolpropane tricaprylate had the following properties:

Oxidative stability (500 F.), percent weight loss 20 Viscosity at 210F., centistokes 5.3

Viscosity at 100 F., centistokes 30.6

Pour point, F. 65

We claim:

A synthetic lubricant composition wherein the lubricant base comprisesat least one keto-ester of formula selected from the group consisting ofCCH2. CH2. 0 02R References Cited by the Examiner UNITED STATES PATENTS2,386,736 10/1945 Bruson 260465.4 X 2,403,570 7/1946 Weist et a1. 2604642,460,536 2/ 1949 Rogers 260465.4 X 3,057,815 10/1962 Bartlett et a1.252-57 X FOREIGN PATENTS 63 8,161 3/1962 Canada.

OTHER REFERENCES Barnes et aL: Lubricating Engineering, August 1957,pages 454-458.

DANIEL E. WYMAN, Primary Examiner.

W. H. CANNON, Assistant Examiner.

